Multi-Piece Body Manufacturing Method Of Hybrid Bit

ABSTRACT

A method of manufacturing a drill bit may include inserting an attachment end of a journal portion into a cavity of a blade portion. The journal portion includes the attachment end; a journal end opposite from the attachment end; and a journal on the journal end extending downward and radially outward from a longitudinal axis of the journal portion. The blade portion includes the cavity extending a distance into the blade portion; and at least one blade extending along the blade portion from adjacent to the cavity to a gauge region of the drill bit. Then, the method includes attaching the journal portion to the blade portion and mounting a roller cone to the journal.

CROSS REFERENCE TO RELATED APPLICATION

This Application claims the benefit to and priority of U.S. ProvisionalApplication 61/922,145 filed on Dec. 31, 2013, the entirety of which isincorporated herein by reference.

BACKGROUND

Historically, there have been two main types of drill bits used fordrilling earth formations, drag bits and roller cone bits. The term“drag bits” refers to those rotary drill bits with no moving elements.Drag bits include those having cutting elements attached to the bitbody, which predominantly cut the formation by a shearing action. Rollercone bits include one or more roller cones rotatably mounted to the bitbody. These roller cones have a plurality of cutting elements attachedthereto that crush, gouge, and scrape rock at the bottom of a hole beingdrilled.

Bit type may be selected based on the primary nature of the formation tobe drilled. However, many formations have mixed characteristics (i.e.,the formation may include both hard and soft zones), which may reducethe rate of penetration of a bit (or, reduce the life of a selected bit)because the selected bit is not as desirable for certain zones. Forexample, both milled tooth roller cone bits and PDC bits can efficientlydrill soft formations, but PDC bits will often have a rate ofpenetration several times higher than roller cone bits.

Drag Bits

Drag bits, often referred to as “fixed cutter drill bits,” include bitsthat have cutting elements attached to the bit body, which may be asteel bit body or a matrix bit body formed from a matrix material suchas tungsten carbide surrounded by a binder material. Drag bits maygenerally be defined as bits that have no moving parts. However, thereare different types and methods of forming drag bits that are known inthe art. For example, drag bits having abrasive material, such asdiamond, impregnated into the surface of the material which forms thebit body are commonly referred to as “impreg” bits. Drag bits havingcutting elements made of an ultra hard cutting surface layer or “table”(often made of polycrystalline diamond material or polycrystalline boronnitride material) deposited onto or otherwise bonded to a substrate areknown in the art as polycrystalline diamond compact (“PDC”) bits.

PDC bits drill soft formations easily, but they may frequently be usedto drill moderately hard or abrasive formations. They cut rockformations with a shearing action using small cutters that do notpenetrate deeply into the formation. Because the penetration depth isshallow, high rates of penetration are achieved through relatively highbit rotational velocities.

Roller Cone Drill Bits

Roller cone drill bits may be used to drill formations that fail moreefficiently by crushing and gouging as opposed to shearing. Roller conedrill bits are also used for heterogeneous formations that initiatevibration in drag bits. Roller cone drill bits include milled tooth bitsand insert bits. Milled tooth roller cone bits may be used to drillrelatively soft formations, while insert roller cone bits are suitablefor medium or hard formations. Roller cone drill bits include a bit bodywith a threaded pin formed on the upper end of the bit body forconnecting to a drill string, and one or more legs extending from thelower end of the bit body. The threaded pin end is adapted for assemblyonto a drill string for drilling oil wells or the like. Roller cone bitsmay have better steerability when building curve section of a wellbore.

Hybrid Drill Bits

Both roller cone and drag bits have their own advantages. Due to thedifference in cutting mechanisms and cutting element materials, they arebest suited for different drilling conditions. Roller cone bitspredominantly use a crushing mechanism in drilling, which gives rollercone bits overall durability and strong cutting ability (particularlywhen compared to previous bit designs, including disc bits). Drag bitsuse a shearing mechanism for cutting, which allows higher performance insoft formation drilling than roller cone bits are able to achieve.

Thus, in drilling operations facing mixed formations, using one type ofdrill bit over the other may not be adequate for the entire operation.Hybrid drill bits that use a combination of one or more rolling cuttersand one or more fixed blades have been proposed previously. However,problems arise during the design of these hybrid bits in trying tocombine rolling cutters and fixed blades within a limited amount ofspace.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one aspect, embodiments disclosed herein relate to a method ofmanufacturing a drill bit that includes inserting an attachment end of ajournal portion into a cavity of a blade portion. The journal portionincludes an attachment end; a journal end opposite the attachment end;and at least one journal on the journal end extending downward andradially outward from a longitudinal axis of the journal portion. Theblade portion includes a cavity extending a distance into the bladeportion; and at least one blade extending along the blade portion fromadjacent to the cavity to a gauge region of the drill bit. Uponinsertion of the journal portion into the blade portion, the methodfurther includes inserting the journal portion into the cavity of theblade portion; attaching the journal portion to the blade portion; andmounting a roller cone to each of the at least one journal.

In another aspect, embodiments disclosed herein relate to a method ofmanufacturing a drill bit that includes determining a primary torquetransfer area between a journal portion and a blade portion of amulti-piece bit body and inserting an attachment end of the journalportion into a cavity of the blade portion to form the multi-piece bitbody. The journal portion includes the attachment end; a journal endopposite from the attachment end; at least one journal on the journalend extending downward and radially outward from a longitudinal axis ofthe journal portion; and a locking segment formed of a plurality ofintersecting outer side surfaces around the journal portion between theattachment end and the journal end. A total outer side surface area ofthe locking segment is equal to or greater than the primary torquetransfer area. The blade portion includes the cavity extending adistance into the blade portion; and at least one blade extending alongthe blade portion from adjacent to the cavity to a gauge region of thedrill bit.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a blade portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 2 shows a blade portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 3 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 4 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 5 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 6 shows a journal portion being assembled to a blade portionaccording to embodiments of the present disclosure.

FIG. 7 shows an assembled multi-piece bit according to embodiments ofthe present disclosure.

FIG. 8 shows a diagram of an assembled multi-piece bit according toembodiments of the present disclosure.

FIG. 9 shows a journal portion and a corresponding blade portion of amulti-piece bit body according to embodiments of the present disclosure.

FIG. 10 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 11 shows a journal portion and a corresponding blade portion of amulti-piece bit body according to embodiments of the present disclosure.

FIG. 12 is a perspective view of a bit according to embodiments of thepresent disclosure.

FIG. 13 is a side view of a bit according to embodiments of the presentdisclosure.

FIG. 14 is a perspective view of a bit according to embodiments of thepresent disclosure.

FIG. 15 shows the cutting profile of a bit according to embodiments ofthe present disclosure.

FIG. 16 shows a bottom view of a bit according to embodiments of thepresent disclosure.

FIG. 17 shows a side view of a bit according to embodiments of thepresent disclosure.

FIG. 18 shows the cutting profile of a bit according to embodiments ofthe present disclosure.

FIG. 19 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 20 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 21 shows orientation of a ball passageway in the Y-Z plane.

FIG. 22 shows orientation of a ball passageway in the X-Y plane.

FIG. 23 shows orientation of a ball passageway in the X-Z plane.

FIG. 24 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 25 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 26 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

FIG. 27 shows a journal portion of a multi-piece bit body according toembodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to methods of forminghybrid drill bits having both roller cones and blades. The roller conesmay be radially and/or axially offset from the blades, such that theroller cone portion of the bit mainly cuts the center of a borehole andthe blade portion of the bit mainly cuts the gauge portion of theborehole. For example, at least some of the cutting elements disposed onone or more blades of a bit may be positioned at gauge while each of thecutting elements disposed on the one or more roller cones of the bit maybe positioned a distance inward from the gauge of the bit. By providinga roller cone cutting profile that is at least partially non-alignedwith a blade cutting profile, the roller cone portion may maintainsteerability of the bit and the blade portion may protect wear of theroller cone portion.

Hybrid drill bits formed using methods of the present disclosure mayinclude a hybrid drill bit having a multi-piece bit body with alongitudinal axis extending there through, a plurality of journalsproximate to the longitudinal axis, a roller cone rotatably mounted toeach of the journals, and at least one blade protruding from themulti-piece bit body and extending radially and axially along the bitbody from a first end to a second end, where the first end is radiallyfarther from the longitudinal axis than at least part of the at leastone journal, and where the second end is at a gauge region of the drillbit. For example, a plurality of journals may be disposed at or near thelongitudinal axis of the bit, where each journal has a journal axisextending from the base of the journal through the length of thejournal. A first end of a blade may be positioned a radial distancefarther from the longitudinal axis of the bit than the radial distancefrom the longitudinal axis to the journal axis at its base. In anotherexample, at least one journal may be positioned on a bit cutting facesuch that the base of the journal axis is at a first radial distancefrom the bit longitudinal axis and at least one blade has a first endpositioned at a second radial distance from the longitudinal axis thatis greater than the first radial distance but less than the radialdistance from the bit longitudinal axis to the radially outermost pointof the journal.

In some embodiments, methods of the present disclosure may be used toform a drill bit having a multi-piece bit body with a longitudinal axisextending there through, at least one blade protruding from themulti-piece bit body, where the at least one blade extends an axialdistance along a gauge of the multi-piece bit body and a radial inwarddistance from the gauge towards the longitudinal axis, a plurality ofblade cutting elements disposed on the at least one blade and forming ablade cutting profile. At least one journal extends downwardly from themulti-piece bit body, a roller cone is rotatably mounted to the at leastone journal, and a plurality of roller cone cutting elements aredisposed on each roller cone and form a roller cone cutting profile,where the roller cone cutting profile radially extends from a first endto a second end located a radial distance inward from the gauge. Theblade cutting profile may radially overlaps with the roller cone cuttingprofile.

In some embodiments, methods of the present disclosure may be used toform a drill bit having a multi-piece bit body with a longitudinal axisextending there through, a bit radius measured from a gauge of the bitto the longitudinal axis, at least one blade protruding from themulti-piece bit body. The at least one blade extends an axial distancealong the gauge of the multi-piece bit body and a radial inward distancefrom the gauge towards the longitudinal axis. A plurality of journalsextend downwardly from the multi-piece bit body, and a roller cone isrotatably mounted to each of the journals. The radial inward distanceranges from ⅓ to ¾ of the bit radius.

According to some embodiments, methods of the present disclosure may beused to form a hybrid drill bit having a multi-piece bit body with alongitudinal axis extending there through, at least one blade protrudingfrom the multi-piece bit body, where the at least one blade extends anaxial distance along a gauge of the multi-piece bit body and a radialinward distance from the gauge towards the longitudinal axis. At leastone journal extends downwardly from the multi-piece bit body, where theat least one journal extends a length from a base of the journal, and aroller cone is rotatably mounted to each of the at least one journal.The lowest axial point of the at least one blade is axially lower thanthe lowest axial point of the base of the journal. In some embodimentshaving the lowest axial point of a blade that is axially lower than thelowest axial point of the base of the journal, the blade may axiallyoverlap the lowest axial point of the base of the journal. In otherembodiments having the lowest axial point of a blade that is axiallylower than the lowest axial point of the base of the journal, thejournal may be inset within the bit such that the blade does not axiallyoverlap the lowest axial point of the base of the journal.

Methods of manufacturing a drill bit according to embodiments of thepresent disclosure include obtaining or forming components of amulti-piece bit body and assembling the components. For example, in someembodiments, methods include forming a journal portion and a bladeportion of a multi-piece bit body. The journal portion has an attachmentend, a journal end opposite from the attachment end, and at least onejournal on the journal end extending downward and radially outward froma longitudinal axis of the journal portion. The blade portion has acavity extending a distance into the blade portion and at least oneblade extending along the blade portion from adjacent to the cavity to agauge region of the drill bit. The journal portion may be inserted intothe cavity of the blade portion and attached to the blade portion. Aroller cone may be rotatably mounted to each of the journals extendingfrom the journal portion, either before the journal portion is insertedinto the cavity of the blade portion or after the journal portion isinserted into the cavity of the blade portion.

Blade portions of a multi-piece bit body may be formed from a matrixmaterial or a steel material. For example, according to someembodiments, a blade portion may be formed of steel having 0.15-0.35%carbon by weight, from 0.15-0.2% carbon by weight, or 0.25-0.35% carbonby weight. In some embodiments, a blade portion and blades protrudingfrom the blade portion may be integrally formed together from a steelmaterial, such as 4130 steel, the blade portion including a nozzle bore,a reservoir for lubricant or grease, cutter pockets formed along theblades, a locking pin hole, and a cavity for receiving the journalportion. Blade portions formed of steel may have certain features milledor machined into a desired shape. For example, the shape of the cavitywalls may be machined to have particular dimensions and angles ofintersection. Further, blades integrally formed with a steel bladeportion may be machined into a desired shape.

In some embodiments, the blade portion may be formed of a matrixmaterial, such as a carbide hard phase, e.g., one or more transitionmetal carbides such as tungsten carbide, disposed in binder phase, e.g.,one or more metals selected from Group VIII of the Periodic Table. Bladeportions formed of a matrix material may be formed in a mold, such as bypouring a powdered mixture of matrix material into a mold having thenegative shape of a blade portion, which may then be infiltrated with aninfiltrant or heated to a temperature sufficient to melt the binderphase. For example, an infiltrant, or metallic binder material, areplaced over the matrix powder packed in the mold, and the componentswithin the mold are then heated in a furnace to the flow or infiltrationtemperature of the infiltrant, at which point the melted infiltrantinfiltrates the powdered matrix material. Once cooled, the infiltrantmaterial may form a binder phase of the matrix material. Theinfiltration process that occurs during heating bonds the grains ofmatrix material to each other and to the other components to form asolid bit body that is relatively homogeneous throughout. The matrixpowder may be a powder of a single matrix material such as tungstencarbide, or it may be a mixture of more than one matrix material such asdifferent forms of tungsten carbide, e.g., macrocrystalline tungstencarbide, cast tungsten carbide, carburized (or agglomerated) tungstencarbide, and cemented tungsten carbide. In some embodiments,non-tungsten carbides of vanadium, chromium, titanium, tantalum,niobium, silicon, aluminum or other transition metal carbides may beused. In yet other embodiments, carbides, oxides, and nitrides of GroupIVA, VA, or VIA metals may be used. Further, a matrix powder may includeadditional components such as metal additives. A binder phase may beformed from a powder component mixed in with the powdered matrixmaterial and/or from an infiltrating component, such as cobalt, nickel,iron, chromium, copper, molybdenum, their alloys, or combinationsthereof. For example, in some embodiments, a graphite mold may be packedwith a tungsten carbide powder, which may then be infiltrated with amolten copper-based alloy infiltrant.

Blades may be separately attached or may be formed integrally with theblade portion. Use of separately attached blades may be desired due todifferent material requirements for each component, based on theirstructure, function, manufacturing details, expected loads, etc. Forexample, blades made of one type of steel may be separately attached toa blade portion formed of another type of steel, where the steel used toform the blades may be harder than the steel used to form the remainingblade portion. In another example, blades made of a matrix material maybe separately attached to a blade portion formed of steel.

Blade portions may have cutter pockets formed along the cutting edge ofeach blade. For example, in embodiments having blades formed of a matrixmaterial, cutter pockets may be formed in the blade during the moldingprocess. In such embodiments, cutter displacements are positioned alongthe bottom of the mold (in the position eventually forming the cuttingedge of each blade), and the matrix material is loaded in the mold andover the displacements. Once the matrix material is formed into theblade portion shape through the molding process, the displacements maybe removed to reveal the cutter pockets. In embodiments having bladesformed of a steel material, cutter pockets may be machined into thecutting edge of each blade.

FIG. 1 shows an example of a blade portion of a multi-piece bit bodyaccording to embodiments of the present disclosure. The blade portion1000 has a cutting face end 1001, a connection end 1002 opposite thecutting face end, and a gauge region 1003 defining an outer diameter ofthe bit, between the cutting face end and the connection end. A cavity1004 extends a depth into the blade portion from the cutting face end1001. The cavity 1004 opens at the cutting face end 1001 of the bladeportion and is proximate a central axis of the blade portion. Accordingto embodiments of the present disclosure, a cavity may have two or moregeneral shapes of volume. For example, a cavity may have a generallypolygonal shaped volume at the cavity opening and a generallycylindrical shaped volume a distance away from the opening at the baseof the cavity. Further, cavity 1004 may have a diameter at its openingranging from ⅕ to ⅔ of the diameter of the blade portion 1000.Additionally, the depth of the cavity 1004 may range from 0.3 to 0.8 ofthe axial length of the blade portion. At least one blade 1005 protrudesfrom the blade portion and extends along the blade portion from adjacentto the cavity 1004 to the gauge region 1003 of the drill bit. Aplurality of cutter pockets 1006 are formed along the cutting edge ofeach blade 1005.

Cutting elements may be brazed or otherwise attached to cutter pocketsformed in blades of a blade portion according to embodiments of thepresent disclosure. For example, in some embodiments, blade cuttingelements may be rotatably mounted to cutter pockets formed in theblades, such as by using a retention mechanism to hold the cuttingelement axially within the cutter pocket while still allowing thecutting element to rotate around its axis. Blade cutting elements mayinclude an ultrahard cutting layer, such as a polycrystalline diamond(PCD) layer, thermally stable diamond layer, polycrystalline cubic boronnitride (PCBN) layer, or other superabrasive material layer, which isdisposed on a substrate, such as a carbide substrate. The exposed topsurface of the cutting layer may be referred to as a cutting face, i.e.,the face of the cutting element that contacts and cuts a formation, andthe edge formed by the intersection of the cutting face with the cuttinglayer side surface may be referred to as a cutting edge. Further, bladecutting elements may have planar and/or non-planar cutting faces. Forexample, in some embodiments, blade cutting elements may have a pointedgeometry, a conical shaped geometry, a dome shaped geometry, and/or achisel shaped geometry. In some embodiments, the blade cutting elementsmay have a non-planar upper surface with an elevated crest extendingsubstantially across the diameter of the cutting element (e.g., having asubstantially hyperbolic paraboloid shape or substantially paraboliccylinder shape cutting face geometry). In some embodiments, bladecutting elements may have a planar cutting face. In some embodiments, acombination of blade cutting elements with planar and non-planar cuttingfaces may be used.

A threaded connection may be welded to the connection end of the bladeportion (opposite the cutting face end of the blade portion), which maybe used to attach the bit to a drill string or other tool used indrilling. According to embodiments of the present disclosure, a threadedconnection may be welded to the connection end of a blade portion beforea journal portion is assembled to the blade portion or after the journalportion is assembled to the blade portion. FIG. 2 shows an example of ablade portion made according to embodiments of the present disclosure.As shown, the blade portion 2000 has a cutting face end 2001, aconnection end 2002 opposite the cutting face end, and a gauge region2003 defining an outer diameter of the bit, between the cutting face endand the connection end. A cavity 2004 extends a distance into the bladeportion, and at least one blade 2005 protrudes from the blade portionand extends along the blade portion from adjacent to the cavity 2004 tothe gauge region 2003 of the drill bit. The blade portion 2000 may beformed, for example, from a matrix material using a molding process,such as described above, or from steel, which may be machined to havedesired dimensions and geometries. A plurality of blade cutting elements2007 are attached to cutter pockets formed along the cutting edge ofeach blade 2005. Further, a threaded connection 2008 is welded to theconnection end 2002 of the blade portion. According to some embodimentsof the present disclosure, a threaded connection may be welded to ablade portion before attaching blade cutting elements to the blades inorder to reduce the amount of excess heat exposure to the blade cuttingelements.

Journal portions of a multi-piece bit body may be formed from a steelmaterial. For example, according to some embodiments, a journal portionmay be formed of steel having 0.15-0.35% carbon by weight, from0.15-0.2% carbon by weight, or 0.25-0.35% carbon by weight. Further,steel used to form journal portions may be heat treated or casehardened. The type of steel used to form a journal portion may dependon, for example, the size and shape of the journal portion, the type ofdrilling environment the bit will be exposed to, and the size and shapeof the roller cones that will be mounted to each journal. According tosome embodiments, a journal portion may be formed of 4715, 4815, 8620 or8720 steel. The material used to form a journal portion may be the sameor different as the material used to form a blade portion. According toembodiments of the present disclosure, journal portions may be machinedinto the desired shape, including a journal portion body and at leastone journal protruding from the journal body. Further, upon machiningthe journal portion into the desired shape, the journal portion may beheat treated or case hardened, for example, by carburizing.

FIG. 3 shows an example of a journal portion 3000 having a journalportion body 3001 with a longitudinal axis 3005 extending there through,an attachment end 3002, and a journal end 3003 opposite from theattachment end 3002. The journal end 3003 has a generally polygonalshape, while the attachment end 3002 has a generally cylindrical shape.As used herein, a generally cylindrical shape may include a cylindricalshape having varying diameters. For example, as shown in FIG. 3, thegenerally cylindrical attachment end 3002 includes a larger diametercylindrical portion, a smaller diameter cylindrical portion, and aplurality of grooves 3007 formed in the smaller diameter cylindricalportion (each groove 3007 having a relatively smaller diameter than thediameter of the smaller diameter cylindrical portion. In the embodimentshown, the transition between the journal end 3003 and the attachmentend 3002 is the point along the journal portion length where the changein shape from cylindrical to polygonal occurs. According to someembodiments, a transition from the journal end to the attachment end ofa journal portion may include a change in shape from a polygonal journalend to a cylindrical attachment end. In other embodiments, a transitionfrom the journal end to the attachment end of a journal portion mayinclude a reduced diameter. For example, a journal portion may have apolygonal shaped journal end and a polygonal shaped attachment end witha diameter smaller than the diameter of the journal end. In suchembodiments, the transition between the journal end and attachment endmay be defined as the point or segment along the length of the journalportion that is both axially lower than any journals extending from thejournal portion and that has the reduction in diameter. Further,according to some embodiments, an attachment end of a journal portionmay have a generally continuous shape, while a journal end of thejournal portion may have a non-continuous shape. In such embodiments,the transition between the attachment end and the journal end may bedefined as the point or segment along the length of the journal portionthat changes from the continuous shape to the non-continuous shape. Forexample, a journal portion may have an attachment end with a generallycontinuous cylindrical shape (e.g., a cylinder shape with one or morecircumferential grooves), a journal end with a non-continuous shape,(e.g., a combination of different polygonal shapes), and a transitionbetween the attachment end and the journal end at the point along thejournal portion length where the continuous shape discontinues.

Referring still to FIG. 3, journals 3004 extend downward (i.e., extendin the direction away from the attachment end 3002) and radially outwardfrom the longitudinal axis 3005 of the journal portion. As shown, thejournal end 3003 has two journals 3004 extending therefrom. However,according to other embodiments of the present disclosure, a journalportion may have one journal extending from the journal end, threejournals extending from the journal end, or more than three journalsextending from the journal end. Such embodiments are illustrated inFIGS. 24-27 discussed below. Journals 3004 extend from sloped sidewalls,and as illustrated, at least one sidewall without a slope or with alesser slope extends between the sloped sidewalls from which thejournals 3004 extend. While FIG. 3 shows a non-sloped sidewall extendingbetween either side of the sloped sidewall, it is also within the scopeof the present disclosure that fewer or more non-sloped sidewalls may beused. As discussed below, as a ball passageway extends to such asurface, at least one sidewall without a journal may be incorporated forcone retention. In one or more embodiments, the angle of the slopedsidewalls with respect to a central axis of the journal portion 3000 mayrange from greater than 0 to less than 90 degrees.

The journal end 3003 of the journal portion has a locking segment 3006formed at the base of the journal end, where the locking segment 3006 isformed from a plurality of intersecting outer side surfaces and locatedaxially between the journals 3004 and the attachment end 3002. Thelocking segment 3006 shown has four intersecting outer side surfacesforming a square base (that will face and mate with the blade portionupon insertion of the journal portion into a cavity of blade portion),with the outer side surfaces extending axially away from the base.However, in other embodiments, a journal end may have a locking segmentformed of three intersecting outer side surfaces to form a triangularbase, or a journal end may have a locking segment formed of more thanfour intersecting outer side surfaces; that is, any polygonal base maybe used. Upon inserting a journal portion into a cavity of a bladeportion, a locking segment of the journal portion mates withcorresponding inner surfaces of the cavity, thereby locking the journalportion within the blade portion to inhibit the journal portion fromrotating within the blade portion. For example, the journal portion 3000shown in FIG. 3, having a square shaped locking segment 3006 formed atthe journal end base, may be inserted into a mating cavity of a bladeportion having a square cross-sectional shape. The journal portion 3000further has a locking pin hole 3009 formed along its axial length, wherethe locking pin hole 3009 may receive a locking pin once assembled witha corresponding blade portion. Particularly, once a journal portion isinserted into a corresponding blade portion cavity, a locking pin may beinserted through the blade portion and into a locking pin hole formedwithin the journal portion, thereby locking the journal portion withinthe blade portion. Journal portions may have one or more locking pinholes formed along its length and/or around its perimeter. Further, alocking pin hole may be formed along the attachment end or along thejournal end of a journal portion. For example, as shown in FIG. 3, alocking pin hole 3009 may be formed along the attachment end 3002 of thejournal portion, adjacent to the journal end base. As illustrated,attachment end 3002 includes two segments of substantially cylindricalshapes, having two different radii. The substantially cylindricalsegment adjacent the journal end 3003 may include the locking pin hole3009 and may have a greater radius than the other segment axially spacedfrom the journal end 3003.

The attachment end 3002 of the journal portion 3000 has a plurality ofgrooves 3007 formed around its circumference and along the axial lengthof the attachment end. During the process of assembling the journalportion to a blade portion, an o-ring (not shown) may be disposed withineach groove 3007 formed around the attachment end 3002. O-rings may beformed of various types of sealing materials depending on, for example,the size of the o-ring, the squeeze between the journal portion andblade portion (e.g., the size of the space formed between the groove andthe blade portion cavity), and the amount of pressure. For example,according to some embodiments, an o-ring may be formed of nitrile,highly saturated nitrile (“HSN”), or other types of nitrile butadienerubber (“NBR”), or combinations thereof. Further, the size of an o-ring(e.g., the diameter and/or thickness of the o-ring) may be selecteddepending on, for example, the amount of stretch the material canwithstand before failure, the size of the space formed between thegroove and the blade portion cavity, and the pressure exerted on theo-ring.

The areas defined between adjacent grooves 3007 may be referred toherein as lubrication sections. A lubrication hole 3008 may be formedwithin each lubrication section, which may extend through the body ofthe journal portion 3000 to provide lubricant from the lubrication hole3008 to a retention system formed at the journals (and discussed morebelow). According to embodiments of the present disclosure, prior toinserting a journal portion into a cavity of a blade portion, at leastone o-ring may be disposed around the attachment end of the journalportion, where each o-ring defines a lubrication section. Upon assembly,lubricant may be provided from a lubricant reservoir in a blade portionto a lubrication section formed around the attachment end of thecorresponding journal portion, which may then flow through a lubricationhole and within the journal portion body. The journal portion 3000 shownin FIG. 3 has two lubrication sections formed between three grooves3007. However, in some embodiments, a journal portion may have onelubrication section formed between two adjacent o-rings, or a journalportion may have more than two lubrication sections formed betweenadjacent o-rings.

Referring now to FIGS. 24 and 25, an embodiment of a journal portionhaving three journals (and roller cones) is shown. FIGS. 24 and 25 showsan example of a journal portion 3000 having a journal portion body 3001with a longitudinal axis 3005 extending there through, an attachment end3002, and a journal end 3003 opposite from the attachment end 3002. Thejournal end 3003 has a generally polygonal shape, and in thisillustrated embodiment, a hexagonal cross-sectional. Three journals 3004extend downward (i.e., extend in the direction away from the attachmentend 3002) and radially outward from the longitudinal axis 3005 of thejournal portion, and as illustrated in FIG. 25, may have roller cones3050 mounted and assembled thereon. The attachment end 3002 includes aplurality of grooves 3007 formed around its circumference and along theaxial length of the attachment end, and as illustrated in FIG. 25, aplurality of o-rings 3040 may fit within the plurality of grooves 3007.

Referring now to FIGS. 26 and 27, an embodiment of a journal portionhaving a single journal (and roller cone) is shown. FIGS. 24 and 25shows an example of a journal portion 3000 having a journal portion body3001 with a longitudinal axis 3005 extending there through, anattachment end 3002, and a journal end 3003 opposite from the attachmentend 3002. The journal end 3003 has a generally cylindrical shape, havingan angled slice cut therethrough. A single journal 3004 extends downward(i.e., extend in the direction away from the attachment end 3002) andradially toward the longitudinal axis 3005 of the journal portion fromthe angled surface of the journal portion, and, as illustrated in FIG.27, may have a roller cone 3050 mounted and assembled thereon. Theattachment end 3002 includes a plurality of grooves 3007 formed aroundits circumference and along the axial length of the attachment end, andas illustrated in FIG. 27, a plurality of o-rings 3040 may fit withinthe plurality of grooves 3007.

Referring now to FIGS. 4 and 5, an assembly of roller cones to a journalportion is shown. Particularly, FIG. 4 shows a journal portion 4000having a journal portion body 4001 with a longitudinal axis 4005extending there through, an attachment end 4002, and a journal end 4003opposite from the attachment end 4002. Journals 4004 extend in thedirection away from the attachment end 4002 and radially outward fromthe longitudinal axis 4005 of the journal portion. Each journal 4004extends from a journal surface 4012 of the journal end 4003, and atransition surface 4013 extends between the journal surfaces 4012.Journal surfaces 4012 are sloped with respect to the journallongitudinal axis 4005, while transition surfaces 4013 are non-slopedwith respect to the journal longitudinal axis 4005 (the transitionsurfaces 4013 are parallel with the journal longitudinal axis 4005).However, according to embodiments of the present disclosure, transitionsurfaces may be sloped or non-sloped. Further, a journal end may includeone or more transition surfaces and one or more journal surfaces.

As shown, the journal end 4003 of the journal portion has asquare-shaped locking segment 4006 formed at the base of the journalend. The locking segment 4006 is formed by four intersecting outer sidesurfaces and located axially between the journals 4004 and theattachment end 4002. The attachment end 4002 of the journal portion 4000has a plurality of grooves formed around its circumference and along theaxial length of the attachment end. An o-ring 4007 is disposed withineach groove. The area between adjacent o-rings 4007, which may bereferred to as a lubrication section, has a lubrication hole 4008opening formed therein, and a lubrication hole 4008 may be present ineach lubrication section. A lubrication channel 4011 extends from thelubrication hole 4008 formed in each lubrication section, through thebody of the journal portion 4000, and to a retention system formed atthe journal end 4003. As shown, the retention system includes a ballpassageway 4009 extending from an opening formed at the journal end 4003to a journal race 4010, where the lubrication hole 4008 intersects withthe ball passageway 4009. Particularly, ball passageway 4009 extendsfrom an opening formed at a transition surface 4013 of the journal end.In other embodiments, a ball passageway may extend from one journalsurface to a journal extending from a second journal surface, dependingon the size and configurations of the journal surfaces and the size ofthe journals, for example.

Roller cones 4015 may be retained to the journals 4004 by fitting aplurality of retention balls into a ball race formed between the journalrace 4010 and a corresponding roller cone race. Particularly, theretention balls may be inserted through the ball passageway 4009 to theball race formed between each journal 4004 and roller cone 4015, whereeach ball passageway 4009 extends through the journal end 4003 to eachjournal race 4010. For example, in some embodiments, a roller cone 4015may first be fitted on a journal 4004, and then a plurality of retentionballs may be inserted through a ball passageway 4009 to fit in the ballrace formed between the journal race 4010 and corresponding roller conerace. Retention balls may be retained in the ball races by a ballretainer (not shown), which may be inserted into the ball passageway4009 after the retention balls, and then secured in place (such as by aplug welded in place). The retention balls may carry any thrust loadstending to remove the roller cone 4015 from the journal 4004 and therebyretain the roller cone on the journal. Further, lubricant providedthrough the lubrication hole 4008 may flow to the ball passageway 4009and into the ball race to provide lubrication to the retention balls.

The direction of the ball passageway 4009 extension through the journalend to the journal race 4010 may be defined by a BHP breakout angle, aBHP 45 angle, and a BHP twist angle. The BHP breakout angle, BHP 45angle and BHP twist angles may be defined with respect to a journallongitudinal axis and a journal portion longitudinal axis. Referring toFIG. 21, a BHP breakout angle refers to the angle α formed between theball passageway 1609 and the z-axis when viewed along the Y-Z plane.According to some embodiments, a ball passageway may have a BHP breakoutangle ranging from about 0 degrees to about 45 degrees, and in someembodiments, the BHP breakout angle may range from about 20 degrees toabout 30 degrees. Referring now to FIG. 22, the BHP 45 angle refers tothe angle β formed between the ball passageway 1609 and the y-axis whenviewed along the X-Y plane. According to some embodiments, a ballpassageway may have a BHP 45 angle ranging from about 0 degrees to about45 degrees, and in some embodiments, the BHP breakout angle may rangefrom about 20 degrees to about 30 degrees. Referring now to FIG. 23, theBHP twist angle refers to the angle of rotation γ around the journallongitudinal axis formed between the ball passageway 1609 and the x-axiswhen viewed along the X-Z plane. According to some embodiments, a ballpassageway may have a BHP twist angle ranging from about 0 degrees toabout 45 degrees, and in some embodiments, the BHP breakout angle mayrange from about 20 degrees to about 30 degrees.

Roller cones may include bodies having a rounded, a conical, or a discshape and a plurality of cutting elements disposed thereon. For example,as shown in FIG. 5, a roller cone 4015 has a frustoconical shaped bodywith a plurality of cutting elements 4016 disposed thereon. Roller conesizes may differ with respect to one or more of a roller cone's outerradius, nose projection, radius of curvature, etc. As shown, the rollercone 4015 has at least four circumferential rows of cutting elements4016. However, other embodiments may have more or less than four rows ofcutting elements. Further, roller cones may have cutting elementsdisposed thereon in arrangements other than in rows.

Roller cones may have various types of roller cone cutting elementsdisposed thereon. For example, in some embodiments, roller cone cuttingelements may be formed integrally with the roller cone (and formed ofthe same base material of the roller cone), which may be referred to asmilled teeth. In other embodiments, roller cone cutting elements may bepress fitted (interference fitted) or otherwise attached within holesformed around the roller cones. Roller cone cutting elements may beformed of, for example, carbide materials, such as tungsten carbide,natural or synthetic diamond, boron nitride, or any one or combinationof hard or superhard materials. For example, roller cone cuttingelements may include tungsten carbide inserts, diamond enhanced inserts,or PCBN inserts.

Referring now to FIG. 6, assembly of a journal portion 6000 to a bladeportion 6050 is shown. The journal portion 6000 has a journal portionbody 6001 with an attachment end 6002 and a journal end 6003 oppositefrom the attachment end 6002. Attachment end 6002 has a generallycylindrical shape, while the journal end 6003 has a generally polygonalshape. Journals (not shown) extend in the direction away from theattachment end 6002 and radially outward from the journal end 6003, anda roller cone 6015 is rotatably mounted to each journal. A plurality ofroller cone cutting elements 6016 are attached to the roller cones 6015.The attachment end 6002 of the journal portion 6000 has a plurality ofo-rings 6007 disposed within grooves formed along the axial length ofthe attachment end 6002. Lubrication sections formed between adjacento-rings 6007 each have a lubrication hole 6008 opening formed therein. Alubrication channel extends from the lubrication hole 6008, through thebody of the journal portion 6000, to a retention system formed at thejournal end 6003 to retain a roller cone 6015 to a journal. For example,the retention system may include a ball passageway extending from anopening formed at the journal end to a ball race formed between ajournal race and a corresponding roller cone race, where the lubricationhole intersects with the ball passageway. A plurality of retention ballsmay be inserted through the ball passageway and into the ball race toretain the roller cone to the journal.

According to some embodiments of the present disclosure, a journalportion may have a number of lubrication sections, each with alubrication hole formed therein, equal to the number of roller conesmounted thereto. For example, in some embodiments, a journal portionhaving two roller cones, each mounted to a journal extending from thejournal end, may have two lubrication sections defined between threeo-rings, where each lubrication section has a lubrication hole toprovide lubrication to each of the two retention systems used to retainthe roller cones to the journals. In other embodiments, a journalportion may have a number of lubrication sections different from thenumber of roller cones mounted thereto. For example, more than onelubrication hole may be formed in a lubrication section, where eachlubrication hole provides lubrication to separate retention systems usedto retain roller cones to journals.

The blade portion 6050 has a cutting face end 6051, a connection end6052 opposite the cutting face end, and a gauge region 6053 defining anouter diameter of the bit, between the cutting face end and theconnection end. A cavity 6054 extends a distance into the blade portion,and at least one blade 6055 protrudes from the blade portion and extendsalong the blade portion from adjacent to the cavity 6054 to the gaugeregion 6053 of the drill bit. The at least one blade 6055 may extendradially and axially along the blade portion from a first end to asecond end, where the first end is at a radial distance from the cavity6054, the distance ranging from 0 to 20% of the bit diameter, and thesecond end is at the gauge region 6053 of the drill bit. Further, thecutting face end 6051 may be designed to accommodate roller cones 6015mounted to the journal portion 6000 once the journal portion 6000 isassembled with the blade portion 6050. For example, the size, number andposition of the blades 6055 may be designed to provide enough space forthe roller cones 6015 to extend a radial distance across the cuttingface end 6051 of the blade portion 6050. A plurality of blade cuttingelements 6057 are attached to cutter pockets formed along the cuttingedge of each blade 6055.

The blade portion 6050 has at least one lubrication reservoir 6056,where a passage (not shown) extends through the blade portion, from thelubrication reservoir 6056 to the cavity 6054. Upon attaching thejournal portion 6000 to the blade portion 6050, each passage opens toone of the lubrication sections formed along the attachment end 6002 ofthe journal portion 6000, thereby providing a passage for lubrication toflow from each lubrication reservoir to a lubrication hole 6008 formedin each lubrication section, which may then flow through the lubricationholes 6008 to the retention systems used to retain the roller cones 6015to journals. In other words, according to embodiments of the presentdisclosure, a journal portion may fit within a cavity of a bladeportion, such that one or more passages extending from a lubricationreservoir align with lubrication sections formed around the attachmentend of the journal portion. In some embodiments, the journal portion maybe aligned within a blade portion using the mating shapes of a lockingsegment formed around the journal portion and the cavity formed in theblade portion.

According to embodiments of the present disclosure, a journal portionmay include a locking segment formed by a plurality of intersectingouter side surfaces, and upon inserting the journal portion into acavity formed in a blade portion, the locking segment mates with aplurality of inner surfaces of the cavity. For example, as shown in FIG.6, the journal end 6003 of the journal portion has a square-shapedlocking segment 6006 formed at the base of the journal end. The lockingsegment 6006 is formed by four intersecting outer side surfaces andlocated axially between the roller cones 6015 and the attachment end6002. The cavity 6054 formed in the blade portion 6050 has fourintersecting inner surfaces 6059 defining a locking segment receivingvolume. The locking segment receiving volume corresponds in size andshape to the locking segment 6006 of the journal portion 6000. Thus,when the journal portion 6000 is assembled with the blade portion 6050,the locking segment 6006 of the journal portion 6000 mates with thecorresponding inner surfaces 6059 of the cavity 6054 formed in the bladeportion 6050. The embodiment shown in FIG. 6 has a locking segment 6006formed of four intersecting outer side surfaces and a cavity 6054 withfour mating intersecting inner surfaces 6059. However, other embodimentsmay have a locking segment formed of more or less than four intersectingouter side surfaces and a cavity with corresponding intersecting innersurfaces. By forming a locking segment and corresponding portion of acavity with intersecting, or angled, side surfaces, the locking segmentmay be rotationally locked within the cavity. In other words, the anglesformed by the intersecting side surfaces in the corresponding shapes ofthe locking segment and cavity may prevent the locking segment, and thusthe journal portion, from rotating within the blade portion cavity.

Cavity 6054 further includes an attachment end receiving volume 6060defined by one or more inner surfaces located a distance from the cavityopening and at a greater depth than the locking segment receivingvolume. As shown, the attachment end receiving volume 6060 has agenerally cylindrical shape, defined by cylindrical inner surfaces withmultiple radii corresponding with varying radii of the attachment end6002 of the journal portion 6000. According to embodiments of thepresent disclosure, a cavity may include two or more volumes havingdifferent shapes or sizes that correspond with the locking segment andattachment end of a journal portion.

Further, FIG. 6 shows locking pins 6009 inserted into locking pin holesformed along the journal body 6001, which may be used to lock thejournal portion 6000 to the blade portion 6050. The locking pins areshown in FIG. 6 as being disposed in the locking pin holes prior to thejournal portion being inserted into the blade portion 6050 cavity 6054in order to show configuration of locking pins 6009 with respect to thejournal portion 6000. However, according to embodiments of the presentdisclosure, the locking pins 6009 are inserted into locking pin holesformed in the journal portion 6000 after inserting the journal portion6000 into the blade portion 6050. Particularly, the journal portion 6000may be inserted into the cavity 6054 of the blade portion 6050 such thatblade locking pin holes 6058 align with the locking pin holes formed inthe journal portion 6000. The locking pins 6009 may then be insertedthrough the blade locking pin holes 6058 and into the locking pin holesformed in the journal portion 6000, such that the locking pins 6009extend through the blade portion 6050 and at least partially into thejournal portion body 6001. Locking pins 6009 may have a length equal tothe combined length of a blade locking pin hole 6058 and correspondingjournal portion locking pin hole. Further, a locking pin hole formed inthe journal portion may extend from ⅛ of the diameter of the journalportion to the entire diameter of the journal portion. For example, inembodiments having a journal portion locking pin hole that extends theentire diameter of journal portion, a locking pin may have a lengthequal to or greater than the combined length of a blade portion lockingpin hole and the diameter of the journal portion, such that the lockingpin may be inserted through the blade portion locking pin hole andthrough the entire diameter of the journal portion.

FIG. 7 shows a journal portion 7000 assembled with a blade portion 7050according to embodiments of the present disclosure. The journal portion7000 has an attachment end (not shown) and a journal end opposite fromthe attachment end, where roller cones 7015 are rotatably mounted tojournals extending from the journal end. A plurality of roller conecutting elements 7016 are attached to the roller cones 7015. The bladeportion 7050 has a cutting face end 7051, a connection end 7052 oppositethe cutting face end, and a gauge region 7053 defining an outer diameterof the bit, between the cutting face end and the connection end. Acavity (not shown) extends a distance into the blade portion, where aportion of the journal portion 7000 is inserted into the cavity. Atleast one blade 7055 protrudes from the blade portion 7050 and extendsalong the blade portion from adjacent to the journal portion 7000 to thegauge region 7053 of the drill bit. According to embodiments of thepresent disclosure, at least one blade 7055 may extend radially andaxially along the blade portion 7050 from a first end to a second end,where the first end is at a radial distance from the journal portionranging from 0 to 20% of the bit diameter and the second end is at thegauge region 7053 of the drill bit. A plurality of blade cuttingelements 7057 are attached to cutter pockets formed along the cuttingedge of each blade 7055.

The blade portion 7050 has at least one lubrication reservoir 7056,where a passage (not shown) extends through the blade portion, from thelubrication reservoir 7056 to the inserted part of the journal portion7000 in order to provide lubrication to the retention systems used toretain the roller cones 7015 to the journals, such as described above.Further, locking pins 7009 are inserted through blade locking pin holes7058 formed in the blade portion 7050 and into corresponding locking pinholes formed in the journal portion 7000. Particularly, the journalportion 7000 may be inserted into the cavity of the blade portion 7050such that blade locking pin holes 7058 align with the locking pin holesformed in the journal portion 7000. The locking pins 7009 may then beinserted through the blade locking pin holes 7058 and into the lockingpin holes formed in the journal portion 7000, such that the locking pins7009 extend through the blade portion 7050 and at least partially intothe journal portion. The locking pins 7009 may be secured within theblade locking pin holes 7058 by welding the exposed portion of thelocking pins 7009 to the outer surface of the blade portion 7050, suchas by spot welding, friction stir welding, or other conventional weldingmethods known in the art.

FIG. 8 shows a diagram of a journal portion 8000 assembled to a bladeportion 8050 according to embodiments of the present disclosure. Thejournal portion 8000 has an attachment end 8002 and a journal end 8003opposite from the attachment end 8002. Journals 8004 extend downward andradially outward from the journal end 8003, and a roller cone 8015 isrotatably mounted to each journal. A plurality of roller cone cuttingelements 8016 are attached to the roller cones 8015. The attachment end8002 of the journal portion 8000 has a plurality of o-rings 8007disposed within grooves formed along the axial length of the attachmentend 8002. Lubrication sections formed between adjacent o-rings 8007 eachhave a lubrication channel 8008 extending from a lubrication hole formedin the attachment end 8002, through the body of the journal portion8000, to a retention system formed at the journal end 8003 to retain aroller cone 8015 to a journal 8004. The retention system includes a ballpassageway 8011 extending from an opening formed at the journal end 8003to a ball race formed between a journal race 8012 and a correspondingroller cone race, where the lubrication channel 8008 intersects with theball passageway 8011. A plurality of retention balls may be insertedthrough the ball passageway 8011 and into the ball race to retain theroller cone 8015 to the journal 8004.

The blade portion 8050 has a cutting face end 8051, a connection end8052 opposite the cutting face end, and a gauge region 8053 defining anouter diameter of the bit, between the cutting face end and theconnection end. A cavity 8054 extends a distance into the blade portion,where a portion of the journal portion 8000 is inserted into the cavity.The blade portion 8050 has at least one lubrication reservoir 8056, anda passage 8057 extends through the blade portion, from the lubricationreservoir 8056 to the inserted part of the journal portion 8000. Thejournal portion 8000 is inserted into the cavity 8054 such that thepassage 8057 aligns with the hole to the lubrication passageway 8008,thereby providing lubrication from the lubrication reservoir 8056 in theblade portion 8050 to the retention systems in the journal portion 8000used to retain the roller cones 8015 to the journals 8004.

Locking pins 8009 are inserted through blade locking pin holes formed inthe blade portion 8050 (e.g., between blades) and into correspondinglocking pin holes formed in the journal portion 8000. Particularly, thejournal portion 8000 may be inserted into the cavity of the bladeportion 8050 such that blade locking pin holes align with the lockingpin holes formed in the journal portion 8000. The locking pins 8009 maythen be inserted through the blade locking pin holes and into thelocking pin holes formed in the journal portion 8000, such that thelocking pins 8009 extend through the blade portion 8050 and at leastpartially into the journal portion 8000.

According to embodiments of the present disclosure, a method ofmanufacturing a hybrid drill bit may include determining a primarytorque transfer area between a journal portion and a blade portion of amulti-piece bit body and obtaining or forming the journal portion andthe blade portion. The journal portion may be formed, such as bymachining, to have an attachment end, a journal end opposite from theattachment end, at least one journal on the journal end extendingdownward and radially outward from a longitudinal axis of the journalportion, and a locking segment formed of a plurality of intersectingouter side surfaces around the journal portion between the attachmentend and the journal end, where a total outer side surface area of thelocking segment is equal to (e.g., approximately equal to) the primarytorque transfer area. The blade portion may be formed, such as with amolding process and/or by machining, to have a cavity extending adistance into the blade portion and at least one blade extending alongthe blade portion from adjacent to the cavity to a gauge region of thedrill bit. Upon forming the journal portion and the blade portion, theattachment end of the journal portion may be inserted into the cavity ofthe blade portion to form the multi-piece bit body.

FIG. 9 shows a disassembled multi-piece bit body according toembodiments of the present disclosure. The journal portion 9000 has anattachment end 9002, a journal end 9003 opposite from the attachmentend, at least one journal (not shown) extending from the journalportion, on which roller cones 9015 are rotatably mounted, and a lockingsegment 9006 formed of a plurality of intersecting outer side surfaces9007 around the journal portion between the attachment end and thejournal end. A total outer side surface area of the locking segment isequal to or greater than a predetermined primary torque transfer area.The blade portion 9050 has a cutting face end 9051, a connection end9052 opposite the cutting face end, and a gauge region 9053 defining anouter diameter of the bit, between the cutting face end and theconnection end. A cavity 9054 extends a distance into the blade portion,and at least one blade 9055 extends along the blade portion fromadjacent to the cavity 9054 to a gauge region 9053 of the drill bit. Thecavity 9054 has a plurality of intersecting inner surfaces 9059 thatcorrespond to the shape of the intersecting outer side surfaces 9007 ofthe journal portion locking segment 9006.

Upon assembling the journal portion 9000 to the blade portion 9054,various torque forces may be exerted between the journal portion and theblade portion during rotation and contact with other surfaces (e.g.,during drilling a formation). For example, different rotational forcesmay be experienced by a blade portion and a journal portion of amulti-piece bit body during drilling. As one portion experiences higherrotational forces, that portion may apply torque to the other portion,causing coinciding rotation of the different portions of the multi-piecebit body. According to embodiments of the present disclosure,corresponding rotation between different portions of a multi-piece bitbody may be achieved using interlocking shapes between the differentportions, where selected torque forces between the interlocking portionsmay be calculated prior to manufacturing or obtaining the multi-piecebit body. Calculating torque parameters prior to manufacturing orobtaining a multi-piece bit body may allow a manufacturer to design theinterlocking shapes and surfaces of the different multi-piece bit bodyportions based on predicted torque forces. For example, according toembodiments of the present disclosure, torque forces may be predictedfor a multi-piece bit body formed of components (e.g., blade portions,journal portions and locking pins) having a selected shape and size,where predicting may be performed using simulations of the multi-piecebit body and/or using calculations of certain torque forces experiencedbetween the selected components. Based on the predicted torque forces, abit manufacturer may then alter or re-design the multi-piece bit body toimprove bit performance, for example, by altering the shape or size ofone or more multi-piece bit components or by using a different materialto form one or more of the components. The steps of predicting andaltering may be performed more than once.

Referring still to FIG. 9, a primary torque transfer force may becalculated based on a primary torque plane formed between the matingintersecting outer side surfaces 9007 of the journal portion lockingsegment 9006 and the intersecting inner surfaces 9059 of the cavity9054. The primary torque plane has a total torque transfer contact areaequal to the total surface area of the intersecting outer side surfaces9007 of the journal portion locking segment 9006. In other words, thetotal torque transfer contact area of the locking segment 9006 is equalto the sum of the surface area of each of the four intersecting outerside surfaces 9007. In embodiments having a locking segment formed ofthree intersecting outer side surfaces, the total torque transfercontact area is equal to the total surface area of the three outer sidesurfaces. Embodiments having a locking segment formed of fiveintersecting outer side surfaces have a total torque transfer contactarea equal to the total surface area of the five outer side surfaces;embodiments having a locking segment formed of six intersecting outerside surfaces have a total torque transfer contact area equal to thetotal surface area of the six outer side surfaces; and so forth.According to some embodiments of the present disclosure, a lockingsegment 9006 may have a total torque transfer contact area ranging fromgreater than 1 sq.in. (645.2 sq.mm), greater than 2 sq.in. (1290.3 sqmm), greater than 4 sq.in. (2580.6 sq.mm), greater than 6 sq.in. (3871sq.mm), greater than 8 sq.in. (5161.3 sq.mm), or between 1 sq.in. (645.2sq.mm) and 10 sq.in. (6451.6 sq mm) in other embodiments, however, anysuitable total torque transfer contact area may be used. Further,according to embodiments of the present disclosure, a total torquetransfer contact area may be selected based on torque transfer forcescalculated for a multi-piece bit body. The multi-piece bit body may thenbe formed by machining the size and the shape of a locking segment tohave intersecting outer side surfaces with a sum surface area equal tothe total torque transfer contact area.

Referring now to FIG. 10, a secondary torque transfer force may becalculated based on a lock pin torque capacity. As used herein, a lockpin torque capacity refers to the maximum torque that can be applied toa locking pin on a continual basis and still maintain a normallyexpected fatigue life. As shown in FIG. 10, a journal portion 1100 mayhave an attachment end 1102, a journal end 1103 opposite from theattachment end, at least one journal (not shown) extending from thejournal portion, on which roller cones 1105 are rotatably mounted, and alocking segment 1107 formed of a plurality of intersecting outer sidesurfaces around the journal portion between the attachment end and thejournal end. Two locking pins 1109 are inserted into locking pin holesformed in the attachment end 1102 of the journal portion, proximate thelocking segment 1107. However, other embodiments may have one lockingpin or more than two locking pins. The lock pin torque capacity of eachlocking pin 1109 may be calculated using the cross sectional area of thelocking pin 1109, the torque section radius, and the material yieldstrength of the material forming the locking pin 1109. For example, amaterial yield strength of a locking pin 1109 formed of 4815 steel maybe about 124 ksi. However, other embodiments may include locking pinsformed of other types of steel. The torque capacity of a locking pin maybe calculated using the equation:

(torque section radius)×(cross sectional area of the lockingpin)×(material yield strength)/2.

In one or more embodiments, the torque capacity may range from 0.5kft.lb (677.9 Nm) to 10 kft.lb (13560 Nm), with a cross-sectional arearanging from 0.1 sq.in (645.2 sq.mm) to 0.8 sq.in (5161.3 sq.mm), and aradius of ¼ to ⅔ the bit radius.

Further, according to embodiments of the present disclosure, weight onbit (“WOB”) forces may be exerted between a journal portion and a bladeportion of a multi-piece bit body during drilling. For example, aprimary weight on bit force may be calculated based on a weight on bittransfer plane formed between a journal portion and a blade portion of amulti-piece bit body. Calculating weight on bit forces of a multi-piecebit body design prior to manufacturing the multi-piece bit body mayallow a manufacturer to re-design or alter the design of the multi-piecebit body components in order to optimize performance of the multi-piecebit body. According to embodiments of the present disclosure, weight onbit forces may be predicted for a multi-piece bit body, such as bysimulating performance of the multi-piece bit body and/or by calculatingcertain forces experienced between selected components of themulti-piece bit body. Based on the predicted weight on bit forces, a bitmanufacturer may then alter or re-design the multi-piece bit body toimprove bit performance, for example, by altering the shape or size ofone or more multi-piece bit components or by using a different materialto form one or more of the components. The steps of predicting andaltering may be performed more than once.

For example, referring now to FIG. 11, a primary weight on bit transferforce may be predicted between a journal portion 1110 and a bladeportion 1150 of a multi-piece bit body. The journal portion 1110 has anattachment end 1112, a journal end 1113 opposite from the attachmentend, at least one journal (not shown) extending from the journalportion, on which roller cones 1115 are rotatably mounted, and a lockingsegment 1116 formed of a plurality of intersecting outer side surfacesaround the journal portion between the attachment end and the journalend. The locking segment 1116 has a base surface 1117, where the basesurface 1117 intersects each of the outer side surfaces at an edge. Theblade portion 1150 has a cutting face end 1151, a connection end 1152opposite the cutting face end, and a gauge region 1153 defining an outerdiameter of the bit, between the cutting face end and the connectionend. A cavity 1154 extends a distance into the blade portion, and atleast one blade 1155 extends along the blade portion from adjacent tothe cavity 1154 to a gauge region 1153 of the drill bit. The cavity 1154has a plurality of intersecting inner surfaces that correspond to theshape of the intersecting outer side surfaces of the journal portionlocking segment 1116 and a support surface 1159 that corresponds to theshape of the base surface 1117 of the locking segment 1116. Thus, uponassembling the journal portion 1110 to the blade portion 1150, theintersecting inner surfaces and support surface 1159 of cavity 1154receives and mates with the locking segment 1116 of the journal portion1110. A weight on bit transfer plane is formed between the base surface1117 and support surface 1159. The weight on bit transfer capacitybetween the journal portion 1110 and blade portion 1150 may becalculated using the contact area of the weight on bit transfer plane(i.e., the area of contact between the base surface 1117 and the supportsurface 1159) and the material yield strength of the material formingthe journal portion 1110. For example, a material yield strength of ajournal portion 1110 formed of 4130 steel may be about 52 ksi. However,other embodiments may include journal portions formed of other types ofsteel. The WOB transfer capacity may be calculated using the equation:(contact area)x(material yield strength). According to embodiments ofthe present disclosure, a weight on bit transfer capacity may range fromgreater than 100 klb, greater than 120 klb, greater than 150 klb, or 100klb to 180 klb in other embodiments. The actual weight on bit transferwhen a hybrid bit is being used may be greater than 30 klb for bit sizeless than 12.25″ and greater than 50 klb for bit size larger than12.25″.

According to embodiments of the present disclosure, a WOB transfer planecontact area may be selected based on a predicted primary WOB transferforce calculated for a multi-piece bit body. For example, a design of ajournal portion and corresponding blade portion may have a WOB transferplane contact area formed between the mating base surface and supportsurface of the journal portion locking segment and blade cavity. Theprimary WOB transfer force for the design may be calculated based on theselected WOB transfer plane contact area and material of the components.A bit designer may then alter or redesign the journal portion and/orblade portion based on the predicted primary WOB transfer force toimprove bit performance. For example, the size of the base surfaceand/or support surface may be altered and/or the type of material usedto form the journal portion and/or blade portion may be altered, therebychanging the predicted primary WOB transfer force between the journalportion and blade portion. The steps of predicting and altering may beperformed once or more than once.

Further, according to embodiments of the present disclosure, multi-piecebit body components may be designed such that the assembled multi-piecebit body has radially and/or axially displaced roller cone and bladecutting profiles. By radially displacing a blade cutting profile from aroller cone cutting profile in a hybrid drill bit according toembodiments of the present disclosure, high inner cutting efficiency maybe provided by the high shear feature of the outwardly facing rollercones, increased steerability may be provided with some rotating cuttingelements contacting the wall of the wellbore, and a wider range offormation drilling may be achieved.

EXAMPLES

An example of a hybrid drill bit formed using methods of the presentdisclosure is shown in FIGS. 12 and 13, which show a top view and a sideview, respectively, of a hybrid drill bit 100. The bit 100 has amulti-piece bit body 110 with a longitudinal axis 112 extending axiallythere through. The bit 100 has a bit cutting face 102, a gauge region138, and a threaded pin end 104 opposite from the bit cutting face 102.The bit cutting face 102 refers to the side of the bit substantiallyfacing in the direction of drilling, and that may engage the bottom holeof the wellbore being drilled. A drill string or other drilling toolsmay be attached to the threaded pin end 104 of the bit, for example, torotate the bit 100. The gauge region 138 of the bit may cut or maintainthe gauge, or outer diameter, of the borehole being drilled, and thusmay engage a sidewall of the wellbore. Bit 100 includes a plurality ofroller cones 120 and a plurality of blades 130 (though other embodimentsmay include one or more roller cones and/or one or more blades) arrangedin such a manner that the roller cones 120 engage with and cut a bottomhole, but do not engage with the sidewall of a wellbore, and blades 130at least engage and cut the sidewall of the wellbore. However, it isalso within the scope of the present disclosure that the blades 130 mayextend through the gauge region 138 and into the bit cutting face 102(thus forming a part of the bit cutting face). Because roller cones 120engage with and cut a bottom hole (and not a side wall), the outerradial extent of the roller cones 120 is radially inside of the bitdiameter, defined by the gauge 138. The extent of overlap betweencutting elements on roller cone 120 and blade 130 depends on the blade130 location, relative to roller cones 120. For example, blades 130.1(illustrated as being at offset from roller cones 120) extend to a moreradially interior position than blades 130.2 (illustrated as beingradially in line with roller cones 120, i.e., a radial plane of theblade overlaps roller cone). As used herein, the terms “upper”,“uppermost” or “above” refer to the direction facing toward the threadedpin end 104 of the bit 100 and the terms “lower”, “lowest” or “below”refer to the direction facing toward the axial end of the bit havingjournals extending therefrom.

The roller cones 120 are each rotatably mounted to a journal (not shown)extending from the multi-piece bit body 110 at the bit cutting face 102.At least one blade 130 protrudes from the bit body 110 and extendsradially and axially along the bit body 110 from a first end 132 to asecond end 134 (illustrated as ending at a heel surface, as that term isknown in the art). As shown, the first end 132 of the blade 130.2 ispositioned along the bit cutting face 102, at a radial distance 136farther from the longitudinal axis 112 than the radially outermostportion of at least one roller cone 120 (and thus farther than thejournal that the roller cone is mounted to). Depending on the size andshape of the bit cutting face 102, the blades 130 may extend a radialdistance along the bit cutting face 102 as well as an axial distancefrom the bit cutting face 102 along a gauge region 138 of the bit 100,where the second end 134 of the blades 130 are at the gauge region 138.Further, at least one of the first ends 132 of the blades 130 and atleast one of the plurality of journals may be positioned within a sharedradial plane 140 (i.e., a plane intersecting the longitudinal axis 112at a perpendicular angle), such that the axial height of the first end132 and the axial height of the journal overlap. In other words, theradial plane 140 may intersect both the first end 132 of a blade 130 andthe journal. In other embodiments, the difference in axial heightbetween at least one journal and at least one blade first end may belarge enough that no radial plane may be shared between the at least onejournal and blade first end.

Referring now to FIG. 14, a top view of a hybrid drill bit 300 having ajournal portion assembled with a blade portion, according to embodimentsof the present disclosure, is shown. The bit has a plurality of journals320 extending from a multi-piece bit body 310 (the journal portionassembled to the blade portion), where each journal 320 has a journalaxis 322 extending from a base of the journal 320 through the length ofthe journal 320. As used herein, a base of a journal may be drawn alonga plane intersecting the journal where it meets the multi-piece bitbody. The journals 320 are positioned at the bit cutting face such thateach of the journal axes 322 are at a first radial distance 325 (at theintersection of the journal axis 322 with the journal portion of themulti-piece bit body 310) from the longitudinal axis 312 of the bit 300.As used herein, the term “first radial distance” refers to the radialdistance measured between the longitudinal axis of a bit and the journalaxis of a journal at its base. As shown, the bit 300 has three journals320 with journal axes 322 at the same first radial distance 325.However, a hybrid drill bit may have more or less than three journals,as well as non-equal first radial distances. For example, in embodimentshaving more than one journal, each axis of the journals may be at anequal radial distance from the bit longitudinal axis, or each axis ofthe journals may be at different radial distances from the bitlongitudinal axis. A first radial distance may range from a lower limitof 0, greater than 0, 1/32, 1/16, ⅛ or ¼ of the bit radius to an upperlimit of ⅛, ¼, ⅓, or ½ of the bit radius, where any lower limit may becombined with any upper limit

Additionally, a plurality of blades 330 extend radially from the bladeportion of the multi-piece bit body 310. Each of the blades 330 extendsaxially along the body 310 from a first end 332 (positioned at the bitcutting face such that the cutting elements thereon may cut and engage awellbore bottom hole) to a second end 334 (at a gauge region of the bitsuch that the cutting elements thereof may cut and engage a side wall ofthe wellbore). Further, blades 330 may have a top face 337 (which facesradially outward from the multi-piece bit body), a leading face 336(which faces in the direction of bit rotation), and a trailing face 338opposite from the leading face 336. The first end 332 of a blade 330 maybe a wall that is radiused or otherwise transitioned from the base ofthe blade (at the multi-piece bit body) to the top face 335. Forexample, a first end 332 may include a sloped, curved, or substantiallyperpendicular wall extending from the multi-piece (e.g., two-piece) bitbody to the top face 335 of the blade 330. The first end 332 of eachblade 330 is at a second radial distance 335 from the longitudinal axis312 (measured from the longitudinal axis 312 to the base of the firstend 332). As shown, the first end 332 of each blade 330 is at an equalsecond radial distance 335 from the longitudinal axis 312. However, thefirst ends of a plurality of blades may be at different radial distancesfrom the longitudinal axis (for example, as illustrated in FIG. 1, whereblades 130 aligned with the roller cones 120 have a larger second radialdistance than blades 130 located between adjacent roller cones 120). Asecond radial distance may range between ¼ and ½ of the bit radius fromthe longitudinal axis. In some embodiments, a second radial distance mayrange from greater than ¼ of the radial distance to the bit gauge fromthe longitudinal axis. In some embodiments, a second radial distance mayrange from greater than ⅓ of the radial distance to the bit gauge fromthe longitudinal axis. In some embodiments, a second radial distance mayrange from greater than ½ of the radial distance to the bit gauge fromthe longitudinal axis. Further, in some embodiments, a second radialdistance may range from greater than ⅔ of the radial distance to the bitgauge from the longitudinal axis. The second radial distance may bedesigned based on the first radial distance to provide an overlappingjournal/blade profile in the radial direction. In such embodiments, inaddition to the first and second radial distances, the journal size andangle of journal extension may also be adjusted such that the radialdistance from the bit longitudinal axis to the radially outermost pointof the journal is larger than the second radial distance.

Referring again to FIGS. 12 and 13, a plurality of blade cuttingelements 135 are disposed on each blade 130, and a plurality of rollercone cutting elements 125 are disposed on each roller cone 120. Asshown, the blade cutting elements 135 have planar cutting faces, whilethe roller cone cutting elements 125 have non-planar cutting faces 125.However, different types of cutting elements may be used on the blades130 and roller cones 120. For example, both blade cutting elements androller cone cutting elements may have planar cutting faces. Cuttingelements used with hybrid drill bits of the present disclosure mayinclude polycrystalline diamond compacts (PDCs), diamond gritimpregnated inserts (“grit hot-pressed inserts” (GHIs)), naturaldiamond, milled steel teeth, tungsten carbide inserts (TCIs), diamondenhanced inserts (DEIs), or conical shaped (or other substantiallypointed) cutting elements.

The blade cutting elements may include primary cutting elements andbackup cutting elements (e.g., elements that “back up” or arerotationally behind a primary cutting element, and having a radialposition approximately equal to that of the primary cutting element). Insome embodiments, the primary and backup cutting elements may be locatedon a single blade, while in other embodiments, the primary cuttingelements may be located on a primary blade (that extends from adjacentthe cavity to the gage) and the backup cutting elements may be locatedon a secondary blade. In other embodiments, primary cutting elements maybe located on both primary and secondary blades (and e.g., no backupcutting elements are used). The primary cutting elements and backupcutting elements may be the same or different. Similarly, the primarycutting elements located on the primary blades and the primary cuttingelements located on the secondary blades may be the same or different.In some embodiments, the primary cutting elements (or primary cuttingelements on the primary blade) may have a planar cutting face and thebackup cutting elements (or primary cutting elements on the secondaryblade) may have a conical shape, and in other embodiments, the primarycutting elements (or primary cutting elements on the primary blade) mayhave a conical shape and the backup cutting elements (or primary cuttingelements on the secondary blade) may have a planar cutting face. In someembodiments, the primary cutting elements (or primary cutting elementson the primary blade) may have a non-planar upper surface with anelevated crest extending substantially across the diameter of thecutting element (e.g., having a substantially hyperbolic paraboloidshape or substantially parabolic cylinder shape), and the backup cuttingelements (or primary elements on the secondary blade) may have a conicalshape, or in other embodiments the primary cutting elements (or primarycutting elements on the primary blade) may have a conical shape, and thebackup cutting elements (or primary elements on the secondary blade) mayhave a non-planar upper surface with an elevated crest extendingsubstantially across the diameter of the cutting element (e.g., having asubstantially hyperbolic paraboloid shape or substantially paraboliccylinder shape). However, any combination of blade cutting elements maybe used in the blade portion and, e.g., different shaped cuttingelements may be included as primary cutting elements on a single blade.

The blade cutting elements 135 form a blade cutting profile, and theroller cone cutting elements 125 form a roller cone cutting profile. Asused herein, a cutting profile (e.g., a blade cutting profile and aroller cone cutting profile) refers to the profile or outline of cuttingelements as they would appear in rotated view, i.e., when the bitrotated about its longitudinal axis and the roller cones are rotatedabout their rotational axes. For example, FIG. 15 shows a cuttingprofile 400 of a hybrid drill bit according to embodiments of thepresent disclosure. The cutting profile 400 includes a blade cuttingprofile 430 and a roller cone cutting profile 420. The roller conecutting profile 420 may extend a radial distance 426 from thelongitudinal axis 412 of the hybrid drill bit or a point near thelongitudinal axis to an outer diameter 427 of the roller cone cuttingprofile 420, and the blade cutting profile 430 may extend a radialdistance 436 from an inner diameter 435 of the blade cutting profile 430to an outer diameter 437 of the blade cutting profile 430. According toembodiments of the present disclosure, the outer diameter 437 of theblade cutting profile 430 may be at the gauge of the bit. The rollercone cutting profile 420 may radially overlap with the blade cuttingprofile 430 within the radial extent of a first row 422 of roller conecutting elements (i.e., the row of cutting elements positioned farthestfrom the roller cone base). In some embodiments, the roller cone cuttingprofile 420 may radially overlap with the blade cutting profile within adistance 446, which may be equal to sin(journal angle)x(diameter of thefirst row). That is, the overlap may range from within the end points ofthat distance 446. For example, a roller cone cutting profile mayradially overlap with the blade cutting profile a distance ranging fromless than 0.1 inches (2.5 mm) in some embodiments and less than 1.5inches (38.1 mm) in some embodiments. According to some embodiments ofthe present disclosure, the roller cone cutting profile may not radiallyoverlap the blade cutting profile. In such embodiments, the roller conecutting profile may be radially adjacent to the blade cutting profile,or the roller cone cutting profile may be located a radial distanceapart from the blade cutting profile. In other embodiments, the bladecutting profile may overlap with the first row cutting element profileof the roller cone cutting profile. Further, in one or more embodiments,the blade cutting profile may overlap with the first row cutting elementprofile, but when considering the roller cone cutting elements that areengaging with the bottom hole, there is no overlap. That is, the overlapis with cutting elements that are rotated in an off-bottom position.However, in one or more other embodiments, the blade cutting profile mayoverlap with roller cone elements that are rotated in an on-bottomposition. The cutting profile of FIG. 15 also includes a central cuttingelement 460.

FIGS. 16-18 show a bottom view, a side view, and a cutting profile ofanother hybrid drill bit formed using methods of the present disclosure.The bit 3200 has a multi-piece bit body 3201, a longitudinal axis 3202extending through the bit body 3201, at least one blade 3210 protrudingfrom the bit body, where the at least one blade 3210 extends an axialdistance along a gauge 3204 of the bit body and a radial inward distancefrom the gauge towards the longitudinal axis 3202, a plurality of bladecutting elements 3212 disposed on the blades 3210 and forming a bladecutting profile, at least one journal (shown in FIG. 18 as 3230)extending downwardly from the bit body 3201, a roller cone 3220rotatably mounted to each journal, and a plurality of roller conecutting elements 3222 disposed on each roller cone 3220 and forming aroller cone cutting profile. As shown, the roller cones 3220 and rollercone cutting elements 3222 disposed thereon do not extend to the gauge3204 of the bit 3200. According to some embodiments of the presentdisclosure, a journal portion may further include a center cuttingelement disposed between the two or more journals extending from thejournal end of the journal portion, as shown in FIG. 16, as well asFIGS. 19 and 20, which show the journal portion of the bit illustratedin FIGS. 16 and 17. For example, in some embodiments, a center cuttingelement 3230 may be disposed along the longitudinal axis of the journalportion 3202, such that a longitudinal axis of the center cuttingelement 3230 is coaxial with the longitudinal axis of the journalportion. In other embodiments, a center cutting element may be disposedin a hole 3232 (shown in FIG. 19) between two or more journals 304 onthe journal end 303 of the journal portion 300, such that the centercutting element 3230 extends from the journal portion 300 in a directionfacing away from the attachment end 302 of the journal portion 300. Acenter cutting element 3230 may be assembled to a journal portion 300,for example, by brazing or interference fitting a cutting element withina cutter hole 3232 formed in the journal portion 300. A center cuttingelement 3230 may be formed of various materials and have various shapesand sizes. For example, in some embodiments, a center cutting elementmay have a conical shaped cutting surface, i.e., the surface that isexposed from the journal portion and that contacts a workpiece surface,where the conical cutting surface has an apex with a radius ofcurvature. In some embodiments, a center cutting element may be formedof a carbide material, a carbide substrate with a diamond layer thereonforming the cutting layer, or other ultrahard material, and combinationsthereof.

FIG. 18 shows a rotated cutting profile view of the bit 3200 shown inFIGS. 16 and 17. As shown, the roller cone cutting elements 3222disposed on the roller cones 3220 form a roller cone cutting profile3224, and the blade cutting elements 3212 form a blade cutting profile3214. The roller cone cutting profile 3224 may extend a radial distancefrom a point near the longitudinal axis 3202 to an outer diameter 3227of the roller cone cutting profile 3224, where the outer diameter 3227of the roller cone cutting profile 3224 is a distance inward from thebit gauge 3204. The blade cutting profile 3214 may extend a radialinward distance from the gauge 3204 of the bit to an inner diameter 3215of the blade cutting profile 3214. The radial distance of the rollercone cutting profile 3224 may radially overlap with the radial inwarddistance of the blade cutting profile 3214 a distance ranging up to ¾ ofthe bit radius (where the bit radius is measured from the longitudinalaxis to the bit gauge).

Further, as shown in FIG. 18, a plurality of the roller cone cuttingelements 3222 along the on-bottom position may radially overlap with aplurality of blade cutting elements 3212 along the on-bottom position.As used herein, an on-bottom position may refer to the position at whichcutting elements contact or extend in the direction towards the bottom,or axially lowest part, of the wellbore. In cases of directionaldrilling, an on-bottom position may refer to the position at whichcutting elements contact or extend towards a formation face in thedirection of drilling As shown, the roller cone cutting profile 3224along the on-bottom position radially extends from a first end 3226 to asecond end 3228, where the second end 3228 is located a radial distanceinward from the gauge 3204 and a radial distance inward from the rollercone outer diameter 3227. The blade cutting profile 3214 along theon-bottom position extends a radial inward distance overlapping with theroller cone cutting profile 3224 along the on-bottom position, where theon-bottom radially overlapping distance 3240 may range from greater thanthe radius of a blade cutting element and/or roller cone cutting elementto less than ¾ of the bit radius. In some embodiments, an on-bottomradially overlapping distance between a roller cone cutting profile anda blade cutting profile may range from greater than ¼ of the bit radius.In some embodiments, an on-bottom radially overlapping distance betweena roller cone cutting profile and a blade cutting profile may range from½ to ¾ of the bit radius.

Referring still to FIG. 18, the roller cones 3220 may have an extensionlength 3221 and a diameter 3223, where the diameter 3223 decreases fromthe roller cone base along the extension length 3221. As shown, theroller cones 3220 may have an extension length 3221 that is equal to orgreater than the largest diameter 3223 along the extension length 3221.According to embodiments of the present disclosure, roller cones mayhave an extension length to diameter ratio ranging from 0.5 to 2, wherethe extension length is measured from the base of the roller cone to theapex (opposite the base) of the roller cone, and where the diameter ismeasured along the widest portion of the extension length. In someembodiments, such as the one shown in FIGS. 16-18, the extension lengthto diameter ratio may range from about 0.7 to 1.1. In some embodiments,the extension length to diameter ratio may range from about 0.5 to 0.8.Further, in embodiments using roller cones with a larger extensionlength to diameter ratio, the roller cone may extend to near or overlapwith the nose region of a blade. As used herein, a nose region of ablade may refer to the region around the point along a convex region ofthe blade profile in rotated profile view at which the slope of atangent to the blade profile is zero. For example, as shown in FIG. 18,the roller cone 3220 extends radially past (and overlaps with) the noseregion 3216 of the blade cutting profile 3214.

Using roller cones with a larger extension length to diameter ratio mayallow for greater cutting profile overlap. For example, according toembodiments of the present disclosure, a blade cutting profile mayradially overlap with a roller cone cutting profile up to the entireradial length of the roller cone cutting profile. In some embodiments, ablade cutting profile may radially overlap with a roller cone cuttingprofile ranging from a lower limit of ⅛, ¼, ⅓ or ½ of the roller coneextension length to an upper limit of ¼, ⅓, ½, ⅔, ¾ or 9/10 of theroller cone extension length, where any lower limit can be used incombination with any upper limit Further, a blade cutting profile mayradially overlap with a roller cone up to the entire roller coneextension length. For example, in some embodiments, a hybrid bit mayinclude a roller cone mounted to a journal positioned at a journal angleof 0 degrees and at least one blade extending axially along the bitgauge and a distance radially inward from the bit gauge, where theroller cone has an extension length less than the bit radius (such thatthe roller cone does not extend to the gauge of the bit), and where theradial inward distance of the blade overlaps the entire roller coneextension length.

According to embodiments of the present disclosure, the radial distancefrom an assembled multi-piece bit longitudinal axis to the radiallyoutermost point of a journal may overlap with the radial distance fromthe bit gauge to the first end of a blade, such that the radial distancefrom the bit longitudinal axis to the radially outermost point of thejournal extends at least to the radius of a first blade cutting element(i.e., a cutting element positioned closest to the first end of theblade). In some embodiments, the radial distance from the bitlongitudinal axis to the radially outermost point of a journal mayextend past at least ¾ of a first blade cutting element in a bladecutting profile. In some embodiments, the radial distance from the bitlongitudinal axis to the radially outermost point of a journal mayextend to at least the entire diameter of a first blade cutting elementin a blade cutting profile. In some embodiments, the radial distancefrom the bit longitudinal axis to the radially outermost point of ajournal may extend past more that the first three blade cutting elementsalong the blade cutting profile (i.e., past the three blade cuttingelement positions radially closest to the bit longitudinal axis), forexample, past four blade cutting elements, past five blade cuttingelements, or more. In embodiments having the radial distance from thebit longitudinal axis to the radially outermost point of a journalextend radially past at least a portion of a first cutting element of ablade cutting profile, a portion of the roller cone cutting profileoverlaps with a portion of the blade cutting profile, such that at leastone roller cone cutting element and at least one blade cutting elementhas shared cutting duties (i.e., may both cut along a shared radialpath). In other words, in embodiments having a portion of the rollercone cutting profile overlap with a portion of the blade cuttingprofile, the radially outermost roller cone cutting elements may haveshared cutting duties with the radially innermost blade cuttingelements. The number of roller cone cutting elements and blade cuttingelements having shared cutting duties may depend on how much radialoverlap the roller cone cutting profile and blade cutting profile have.

Further, in one or more embodiments, the blade cutting profile may format least a gauge region of the bit, and may extend radially inward intowhat would be considered a shoulder region (as that term is used inconventional fixed cutter bits). That is, each blade cutting element isat an axially lower position relative to the radially outer “adjacent”(when viewed in a rotated profile view) blade cutting element. Further,depending on the shape and curvature of blades (and location of cuttingelements), the axially lowermost blade cutting element may not be theradially most interior blade cutting element, as illustrated in FIG. 5,for example. In such an embodiment, the blade cutting profile extendsthrough the shoulder, into what would be considered a nose region.

Radial positions of roller cone and blade cutting profiles may bedesigned based on the axial positions of the roller cone and bladecutting profiles. According to embodiments of the present disclosure,the blade cutting profile may axially overlap the roller cone cuttingprofile by up to 100 percent of the roller cone cutting profile. Forexample, the blade cutting profile may extend an axial distance alongthe bit that axially overlaps with up to ¾ the axial distance of theroller cone cutting profile. In some embodiments, the blade cuttingprofile may extend substantially to the same axial distance as theroller cone cutting profile to overlap with substantially the entireaxial distance of the roller cone cutting profile. In some embodiments,the blade cutting profile may extend an axial distance past the axiallylowest point of the roller cone cutting profile. According toembodiments of the present disclosure, a journal portion and bladeportion cavity may be designed to provide a desired axial overlapbetween the blade cutting profile and roller cone cutting profile. Forexample, in embodiments having a blade cutting profile extending anaxial distance past the axially lowest point of the roller cone cuttingprofile, the journal portion may be designed to have a relatively largerlength than the cavity formed in the corresponding blade portion, theaxial extension of the journals extending from the journal portion maybe increased, and/or the diameter of the roller cones mounted to thejournals may be increased. In embodiments having a blade cutting profileextending an axial distance along the bit that axially overlaps with upto ¾ the axial distance of the roller cone cutting profile, the journalportion may be designed to have a relatively shorter length than thecavity formed in the corresponding blade portion, the axial extension ofthe journals extending from the journal portion may be decreased, and/orthe diameter of the roller cones mounted to the journals may bedecreased.

Embodiments of the present disclosure may include roller cone cuttingprofiles and blade cutting profiles that are axially and radiallypositioned to axially and/or radially overlap. For example, a bit mayhave a blade cutting profile that axially overlaps the lowest axialpoint of the base of a journal, where the roller cone cutting profileradially overlaps the blade cutting profile by at least the radius ofthe first cutting element of the blade cutting profile.

According to embodiments of the present disclosure, a drill bit mayinclude a bit body having a longitudinal axis extending there through,at least one blade extending from the bit body, a plurality of bladecutting elements disposed on the at least one blade, where the bladecutting elements form a blade cutting profile, at least one journalextending downwardly from the bit body, a roller cone rotatably mountedto each of the at least one journals, and a plurality of roller conecutting elements disposed on each roller cone, where the roller conecutting elements form a roller cone cutting profile, and where theroller cone cutting profile extends an axial height greater than theblade cutting profile.

For example, referring again to FIG. 15, a cutting profile 400 of ahybrid drill bit includes a blade cutting profile 430 and a roller conecutting profile 420, where the roller cone cutting profile 420 extendsan axial height 450 greater than the blade cutting profile 430 (i.e.,the roller cone cutting profile 420 extends axially lower than the bladecutting profile 430). The axial height 450 between the roller conecutting profile 420 and the blade cutting profile 430 may range withinthe axial extent of the first row 422 of roller cone cutting elements.In some embodiments, the axial height 450 between the roller conecutting profile 420 and the blade cutting profile 430 may range fromgreater than 0.1 inches (2.5 mm) For example, in some embodiments, theaxial height between a roller cone cutting profile and a blade cuttingprofile may range from about 0 to about 3 inches (76.2 mm), or with alower limit of any of 0.25 (6.35 mm), 0.5 (12.7 mm), 1.0 (25.4 mm), or1.5 inches (38.1 mm), and an upper limit of any of 1.5 (38.1 mm), 2.0(50.8 mm), 2.5 (63.5 mm), 2.75 (69.85 mm) or 3.0 inches (76.2 mm), whereany lower limit can be used with any upper limit In one or moreembodiments, the blade cutting elements may have at least one axialoverlap with at least one roller cone cutting element when that rollercone cutting element is rotated in an on-bottom position.

According to some embodiments of the present disclosure, a hybrid drillbit may include a bit body having a longitudinal axis extending therethrough, at least one blade protruding from the bit body, where the atleast one blade extends an axial distance along a gauge of the bit bodyand a radial inward distance from the gauge towards the longitudinalaxis, at least one journal extending downwardly from the bit body, wherethe at least one journal extends a length from a base of the journal,and a roller cone rotatably mounted to the at least one journal, wherethe lowest axial point of the at least one blade is axially lower thanthe lowest axial point of the base of the journal. In some embodimentshaving the lowest axial point of a blade that is axially lower than thelowest axial point of the base of the journal, the blade may axiallyoverlap the lowest axial point of the base of the journal. In otherembodiments having the lowest axial point of a blade that is axiallylower than the lowest axial point of the base of the journal, thejournal may be inset within the bit such that the blade does not axiallyoverlap the lowest axial point of the base of the journal.

According to some embodiments of the present disclosure, the axialposition of one or more journals and roller cones mounted thereon may beinset from the axial position of one or more blades, such that thelowermost axial position of the blade cutting profile extends axiallylower than the lowermost axial position of the roller cone cuttingprofile. In such embodiments, the blade cutting profile may axiallyoverlap with 100% of the roller cone cutting profile. As used herein,the terms “lowermost” or “downward” refers to a direction facing awayfrom the connection end of a bit and towards the bit cutting face. Insome embodiments having the lowermost axial position of the bladecutting profile extending axially lower than the lowermost axialposition of the roller cone cutting profile, the multi-piece bit bodymay be formed of a journal portion having a total length (measured fromthe end surface of the attachment end to the lowermost point of ajournal extending from the journal end) that is less than the totallength of the corresponding blade portion.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this disclosure. Accordingly, all such modifications areintended to be included within the scope of this disclosure. It is theexpress intention of the applicant not to invoke 35 U.S.C. §112,paragraph 6 for any limitations of any of the claims herein, except forthose in which the claim expressly uses the words ‘means for’ togetherwith an associated function.

What is claimed is:
 1. A method of manufacturing a drill bit,comprising: inserting an attachment end of a journal portion into acavity of a blade portion, the journal portion comprising: theattachment end; a journal end opposite from the attachment end; and ajournal on the journal end extending downward and radially outward froma longitudinal axis of the journal portion, and the blade portioncomprising: the cavity extending a distance into the blade portion; andat least one blade extending along the blade portion from adjacent tothe cavity to a gauge region of the drill bit; attaching the journalportion to the blade portion; and mounting a roller cone to the journal.2. The method of claim 1, wherein prior to inserting the journal portioninto the cavity, the method further comprises disposing at least twoo-rings around the attachment end, each two adjacent o-rings defining alubrication section.
 3. The method of claim 2, wherein a lubricationchannel extends from the lubrication section through the journal portionto the journal end.
 4. The method of claim 2, wherein the blade portioncomprises a lubrication reservoir and a passageway extending from thelubrication reservoir to the cavity, and wherein upon attaching thejournal portion to the blade portion, the passageway opens to thelubrication section.
 5. The method of claim 1, wherein attachingcomprises inserting at least one locking pin through the blade portionand into the journal portion.
 6. The method of claim 1, wherein theblade portion is formed from a different material than the journalportion.
 7. The method of claim 6, wherein the journal portion is formedof a heat treatable steel.
 8. The method of claim 6, wherein the bladeportion is formed of a matrix material.
 9. The method of claim 1,wherein the journal portion further comprises a locking segment formedby a plurality of intersecting outer side surfaces, the locking segmentbeing between the attachment end and the journal end, and wherein uponinserting the journal portion into the cavity, the locking segment mateswith a plurality of inner surfaces of the cavity.
 10. The method ofclaim 1, wherein the end of the at least one blade adjacent to thecavity is at a radial distance of 0 to 20% of the drill bit diameterfrom the cavity.
 11. The method of claim 1, further comprising disposinga center cutting element on the journal portion along the longitudinalaxis of the journal portion.
 12. A method of manufacturing a drill bit,comprising: determining a primary torque transfer area between a journalportion and a blade portion of a multi-piece bit body; and inserting anattachment end of the journal portion into a cavity of the blade portionto form the multi-piece bit body, the journal portion comprising: anattachment end; a journal end opposite from the attachment end; ajournal on the journal end extending downward and radially outward froma longitudinal axis of the journal portion; a locking segment formed ofa plurality of intersecting outer side surfaces around the journalportion, the locking segment being between the attachment end and thejournal end, a total outer side surface area of the locking segmentbeing equal to or greater than the primary torque transfer area, and theblade portion comprising: the cavity extending a distance into the bladeportion; and a blade extending along the blade portion from adjacent tothe cavity to a gauge region of the drill bit.
 13. The method of claim12, further comprising inserting a locking pin through the blade portionand into the attachment end of the journal portion.
 14. The method ofclaim 13, further comprising determining a secondary torque transferbetween the multi-piece bit body, wherein the secondary torque transferis determined using the cross sectional area, the torque section radius,and the material yield strength of the locking pin to calculate a pintorque capacity of the locking pin.
 15. The method of claim 12, furthercomprising designing a weight-on-bit transfer plane, the weight-on-bittransfer plane comprising the contact area between a base surface of thelocking segment and a mating surface of the cavity.
 16. The method ofclaim 12, wherein the locking segment is formed by machining theplurality of intersecting outer surfaces to fit within the cavity. 17.The method of claim 12, wherein the journal portion comprises a ballhole, and the ball hole opens to a race surface of one of the journal.18. The method of claim 12, wherein the journal portion is formed of adifferent material than the blade portion.
 19. The method of claim 12,further comprising welding a threaded connection to the blade portion atan end opposite from the cavity.
 20. The method of claim 12, furthercomprising attaching a roller cone to the journal.